Supercritical hydrocarbon fuel heat exchange simulation device for evaluating third-class boundary conditions

Abstract

The invention belongs to the field of heat energy engineering and fluid mechanics, and provides a supercritical hydrocarbon fuel heat exchange simulation device for evaluating third-class boundary conditions, which comprises an air compressor, an air heater, an inlet monitoring component, an experimental module, an outlet component, a water cooler and an air flow meter which are connected in sequence, the experiment module comprises an internal circular tube, an external cavity, a thermal insulation material, an air outlet thermocouple, a plurality of temperature measuring grooves, a plurality of air thermocouples, an infrared window and a thermal infrared imager. Through the combination of the internal circular tube, the external cavity, the thermal insulation material, the air thermocouple and the thermal infrared imager, a fuel oil and air convection heat exchange environment of the engine under an active thermal protection condition is constructed, and convection heat exchange experiment data in a specific state can be obtained; and the method is also suitable for simulation calculation of convective heat transfer coefficient and flow resistance under third boundary conditions, and provides equipment support for accurate heat management of active cooling in an engine.

Description

Technical Field

[0001] The invention relates to the fields of thermal energy engineering and fluid mechanics, and in particular to a supercritical hydrocarbon fuel heat exchange simulation device for evaluating third-type boundary conditions. Background Art

[0002] In today's field of active thermal protection of aviation engines, thermal management through reasonable planning of cooling sources has always been one of the effective ways. Accurate thermal management is of great significance to improving engine efficiency, ensuring its reliability and extending its service life. As one of the commonly used fuels in engines, the flow heat transfer characteristics of hydrocarbon fuels in the supercritical state are particularly critical to the thermal management design of the engine. Existing studies usually use isothermal boundary conditions under uniform current to simulate and measure the convective heat transfer coefficient and flow resistance of hydrocarbon fuels in micro-circular tubes. However, this method cannot accurately reflect the complex heat transfer environment inside the engine. Especially under active cooling conditions, the convective heat transfer conditions between fuel and air are significantly different from the uniform heat flow boundary conditions. Therefore, in order to better simulate the heat transfer in a real engine, it is necessary to develop a test bench that can simulate the third type of boundary conditions and accurately measure the flow heat transfer characteristics of hydrocarbon fuels in the supercritical state.

[0003] However, the existing supercritical hydrocarbon fuel cracking flow heat transfer test bench has limitations in simulating the real engine environment and cannot provide accurate experimental data and empirical relationships, thus limiting the development of precise thermal management of engine active cooling. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a supercritical hydrocarbon fuel heat exchange simulation device for evaluating the third type of boundary conditions. Through the combination of internal circular tubes, external cavities, insulation materials, air thermocouples and infrared thermal imagers, a convective heat exchange environment between fuel and air under active thermal protection conditions of the engine is constructed, providing equipment support for precise thermal management of active cooling in the engine.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A supercritical hydrocarbon fuel heat exchange simulation device for evaluating the third type of boundary conditions, comprising: an air compressor, an air heater, an inlet monitoring component, an experimental module, an outlet component, a water cooler and an air flow meter connected in sequence; the experimental module comprises: an internal round tube, an external cavity, a heat-insulating material, an air outlet thermocouple, a plurality of temperature measuring grooves, a plurality of air thermocouples, an infrared window and an infrared thermal imager;

[0007] All the air thermocouples are fixed at equal intervals and depths on the outer surface of the external cavity; the air outlet thermocouples are arranged at the outlet position of the external cavity; the temperature measuring grooves are arranged at equal intervals on the surface of the internal round tube; the heat preservation material is arranged on the surface of the internal round tube corresponding to the air outlet thermocouples; the experimental module is cylindrical with both ends partially closed; the infrared window is arranged on the side of the external cavity; the infrared thermal imager is arranged outside the external cavity;

[0008] The air compressor is used to reduce the compression of external air to the target pressure; the air heater is used to heat the high-pressure gas output by the air compressor to a preset temperature; the import monitoring components are used to collect input gas data; the export components are used to collect output gas data; the water cooler is used to cool the gas output by the experimental module; the air flow meter is used to count the air flow data; the air outlet thermocouple is used to measure the average temperature of the outlet of the experimental module using the insulation material; the air thermocouple is used to collect temperature data of preset points through the temperature measuring groove; the infrared thermal imager collects temperature data of the internal circular tube through the infrared window.

[0009] Preferably, the internal circulating medium of the inner circular tube is fuel oil with a maximum cracking temperature of 800K; the fuel oil and the flowing direction of the gas in the outer cavity are opposite.

[0010] Preferably, the outer side of the external cavity is coated with a heat insulating material.

[0011] The present invention discloses the following technical effects:

[0012] The present invention provides a supercritical hydrocarbon fuel heat exchange simulation device for evaluating the third type of boundary conditions. Through the combination of an internal circular tube, an external cavity, a thermal insulation material, an air thermocouple and an infrared thermal imager, the present invention solves the deficiency that the existing equipment usually adopts equal heat flux boundary conditions under uniform current to simulate and measure the convective heat transfer coefficient and flow resistance of hydrocarbon fuel in a micro-circular tube, and realizes the convective heat exchange environment and related temperature data collection of the fuel and air under the active thermal protection conditions of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0014] Figure 1 A structural diagram of a supercritical hydrocarbon fuel heat exchange simulation device provided in an embodiment of the present invention;

[0015] Figure 2 A schematic diagram of an experimental module provided in an embodiment of the present invention;

[0016] Figure 3 A cross-sectional view of the core part of the experimental module provided by an embodiment of the present invention;

[0017] Figure 4 The overall rear side cross-sectional view of the experimental module provided by the embodiment of the present invention;

[0018] Figure 5 The overall front side cross-sectional view of the experimental module provided by the embodiment of the present invention;

[0019] Description of reference numerals:

[0020] 1- Air compressor, 2- Air heater, 3- Imported monitoring components, 4- Experimental module, 5- Export components, 6- Water cooler, 7- Air flow meter, 8- Infrared window, 9- Infrared thermal imager. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The purpose of the present invention is to provide a supercritical hydrocarbon fuel heat exchange simulation device for evaluating the third type of boundary conditions. Through the combination of internal circular tubes, external cavities, insulation materials, air thermocouples and infrared thermal imagers, a convective heat exchange environment between fuel and air under active thermal protection conditions of the engine is constructed, providing equipment support for precise thermal management of active cooling in the engine.

[0023] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Figure 1 The structure diagram of the supercritical hydrocarbon fuel heat exchange simulation device provided by the embodiment of the present invention is as follows: Figure 1 As shown, the present invention provides a supercritical hydrocarbon fuel heat exchange simulation device for evaluating the third type of boundary conditions, comprising: an air compressor 1, an air heater 2, an inlet monitoring component 3, an experimental module 4, an outlet component 5, a water cooler 6 and an air flow meter 7 connected in sequence; the experimental module 4 comprises: an internal round tube, an external cavity, a heat-insulating material, an air outlet thermocouple, a plurality of temperature measuring grooves, a plurality of air thermocouples, an infrared window 8 and an infrared thermal imager 9;

[0025] All the air thermocouples are fixed at equal intervals and depths on the outer surface of the external cavity; the air outlet thermocouples are arranged at the outlet position of the external cavity; the temperature measuring grooves are arranged at equal intervals on the surface of the internal round tube; the heat-insulating material is arranged on the surface of the internal round tube corresponding to the air outlet thermocouples; the experimental module 4 is cylindrical with both ends partially closed; the infrared window 8 is arranged on the side of the external cavity; the infrared thermal imager 9 is arranged outside the external cavity;

[0026] The air compressor 1 is used to reduce the compression of external air to the target pressure; the air heater 2 is used to heat the high-pressure gas output by the air compressor 1 to a preset temperature; the inlet monitoring component 3 is used to collect input gas data; the outlet component 5 is used to collect output gas data; the water cooler 6 is used to cool the gas output by the experimental module 4; the air flow meter 7 is used to count the air flow data; the air outlet thermocouple is used to measure the average temperature of the outlet of the experimental module 4 using the thermal insulation material; the air thermocouple is used to collect temperature data of preset points through the temperature measuring groove; the infrared thermal imager 9 collects the temperature data of the internal circular tube through the infrared window 8.

[0027] Preferably, the internal circulating medium of the inner circular tube is fuel oil with a maximum cracking temperature of 800K; the fuel oil and the flowing gas in the outer cavity flow in opposite directions.

[0028] Preferably, the outside of the external cavity is coated with a heat insulating material.

[0029] Specifically, the third type of boundary conditions refers to the surface heat transfer coefficient between the boundary of the object and the surrounding fluid and the temperature of the surrounding fluid. This embodiment aims to create the third type of boundary conditions for direct convective heat exchange between high-temperature air and the micro-circular tube, so as to simulate the conditions of active thermal protection in a real engine.

[0030] Furthermore, for the commonly used isothermal boundary conditions, the method to calculate its flow resistance is simple, that is, to install differential pressure sensors at the front and rear ends of the micro-circular tube. x First, the outer wall temperature is collected and the inner wall temperature T is calculated by using the one-dimensional cylinder wall heat conduction formula containing the internal heat source. w,in , and then calculate the oil temperature T based on the input heat f , plus the known applied heat flux q x , the heat transfer coefficient along the flow can be calculated according to the following formula:

[0031]

[0032] When the third type of boundary condition is adopted, high-temperature and high-speed air will flow directly over the surface of the micro-circular tube. On the one hand, the high-temperature air completely covers the air thermocouple and part of the compensation line, making it impossible for the potential difference between the two ends of the thermocouple to normally reflect the temperature of the micro-circular tube wall. On the other hand, the air thermocouple may be blown off by the high-speed air. Therefore, a new method should be used to obtain the wall temperature.

[0033] Preferably, the experimental module 4 is as follows Figure 2 As shown in the figure, the micro-circular tube is wrapped with a cylindrical cavity, the cavity is insulated, and the cavity is a channel for high-temperature air to flow through. A certain number of thermocouples are inserted along the air flow direction at the same horizontal position in the channel. The temperature measured by the thermocouples at this time is called T c,x .

[0034] Furthermore, it is proposed to use an infrared thermal imager 9 and observe the outer tube wall temperature through the transparent glass to obtain T w,out , and considering the one-dimensional cylindrical wall heat conduction differential equation, obtain the inner wall temperature T w,in ,refer to Figure 3 Because the solution of the heat conduction differential equation of the cylinder under the third kind of boundary conditions requires knowing the temperature values ​​at two radial locations, the capillary tube is made into a thick-walled tube, such as an inner diameter of 2 mm and an outer diameter of 10 mm, and many small deep holes are machined on it. The wall temperature value at the deep hole can represent the wall temperature at radial positions such as the tiny area near it, and the inner wall temperature can be obtained through one-dimensional heat conduction of the cylinder wall.

[0035] Specifically, the mainstream temperature in the tube is T f The value of needs to be obtained based on thermal balance, and the calculation formula is as follows:

[0036] c f m f (T f,x -T f,inlet )=c a m a (T a,x -T a,inlet )=Q

[0037] The subscript x represents the parameter at the x position along the process, and the goal is to find T f,x , is to find T a,x , which is the average temperature of the air along the way. It is known that in the flow of variable-property air jacket with constant wall temperature, full thermal development will be achieved, that is, the dimensionless temperature difference will no longer change along the flow direction.

[0038]

[0039] at this time

[0040]

[0041] Assuming that in the third type of boundary condition heat exchange between air and fuel through the capillary wall, the variable-property air flowing in the sleeve can also achieve full thermal development, then under certain conditions, the dimensionless temperature difference shape remains fixed after full thermal development.

[0042]

[0043] Among them, T w,x is the outer wall temperature, T c,x is the temperature measured by thermocouples at different positions, and C is a constant. When the input conditions of the experiment remain unchanged, C changes with different radial positions, but does not change with different flow positions x, that is, as long as the radial positions of all thermocouple measuring points are consistent, then C is the same when stable. If C is calculated by some method, there is only one unknown number T at this time. a,x , the equation can be solved. The solution of C is introduced below.

[0044] Furthermore, during the experiment, the wall of the micro-circular tube behind the last thermocouple along the air flow direction is insulated. After the air leaves the cavity, a small diameter channel can be designed as the outlet. Figure 3 , and insert the thermocouple measuring point T a,outlet However, due to the insulation treatment and ignoring the heat loss of the outer cylinder wall, it can be considered that the thermocouple measuring point arranged at the outlet of the air cavity is equal to the average temperature of the mainstream air, that is:

[0045] T a,x =T a,outlet

[0046] At this time, the value of C can be obtained and the temperature T can be measured according to the thermocouples at different positions. c,x Calculate the average air temperature T at this location a,x Finally, the fuel temperature T at different positions in the micro-circular tube is calculated. f,x .

[0047] Heat flux density q at different positions x The solution of is obtained by the following formula:

[0048]

[0049] Where l represents the distance between any two inserted thermocouples. The numerator of this formula calculates the air temperature drop between the two thermocouples, and the denominator calculates the area of ​​the inner wall between the two thermocouples.

[0050] Finally, the convection heat transfer coefficient h along the process is calculated. x .

[0051] refer to Figure 4 and Figure 5, Experimental module 4 includes two components: an experimental cavity and an experimental micro-circular tube. High-temperature and high-pressure air flows in the experimental cavity to simulate the third type of boundary conditions; high-temperature fuel flows in the micro-circular tube. The two flow directions can be modified according to the experimental requirements. Here, the flow directions are temporarily opposite, which is countercurrent.

[0052] Furthermore, the design of the cavity is a cylindrical wall that ensures sealing. For easy disassembly and assembly, the cylindrical wall can be made into a multi-component model with front and rear sections and a middle section separated. In this figure, for the convenience of drawing, the cylindrical wall is modeled as an integral cast. A sufficient number of thermocouples need to be inserted into the cavity for temperature measurement, and the positions of the thermocouple measuring points should be collinear in the axial and flow directions. In order not to affect the air flow direction, the thermocouple size should be slightly smaller. Please weigh the actual parameters to determine the size here. Pay attention to setting certain temperature and pressure measuring points at the inlet and outlet of the cavity to monitor the inlet and outlet temperatures. The thickness of the cavity needs to be evaluated to obtain the pressure limit of the pressure vessel. The outside of the cavity needs to be covered with sufficient insulation material, and the heat loss should be calibrated before the formal experiment.

[0053] Specifically, the experimental micro-circular tube is a thin tube inserted into the cavity. This thin tube has the following characteristics: a series of small grooves along the flow direction are provided on one side of the tube. The thickness of the grooves is not enough to damage the tube wall. Figure 3 Below, these grooves will cooperate with the infrared thermal imager 9 to observe the temperature of the specified positions a and b. The temperature at a represents the temperature of the outer wall surface, and the temperature at b represents the temperature at the groove. The heat conduction differential equation of the three-dimensional heat-conducting single-layer cylindrical wall is as follows:

[0054]

[0055] Since the amount of heat transfer in the circumferential and axial directions can be ignored and the thermal conductivity is assumed to be a constant, the original equation is simplified to:

[0056]

[0057] The corresponding boundary conditions are r = r1, t = t1, r = r2, t = t2, which can be solved to get

[0058]

[0059] It can be seen from the above formula that the temperature of the inner wall of the micro-circular tube can be solved by the two different radial temperatures observed by the infrared thermal imager 9. The infrared thermal imager 9 collects infrared rays emitted at different temperatures based on the lens and decodes different temperatures. Therefore, the infrared thermal imager 9 lens must directly capture the image inside the temperature sampling groove. In order to achieve this goal, it is necessary to open a hole on the outside of the cavity aligned with the position of the temperature sampling groove, leave space for the thermal imaging lens to shoot, and install a high-temperature resistant lens. Insulation material is placed near the outlet of the air cavity on the outer wall of the micro-circular tube. The insulation material is used to meet the temperature measurement at the cavity outlet Thermocouple is the average temperature of the thermocouple at the end of the air flow.

[0060] Specifically, in order to realize the high-temperature and high-pressure air simulation of the experimental module 4, a complete system needs to be configured for it, in which the air compressor 1 compresses the air and then passes it into the air heater 2 to heat the temperature to the specified temperature, and then transport it to the cavity. The inlet monitoring component 3 and the outlet component 5 are monitoring components for the inlet and outlet air, which can monitor parameters such as temperature and pressure. After the heat exchange is completed, it enters the water cooler 6 for cooling, and then enters the air flow meter 7 to measure the air flow data before being discharged. It should be noted that due to the small size of the experimental module 4, the system can also be changed to a pressure-stabilizing gas tank to discharge air, and then enter the cavity through an electric heating system. This method is more convenient to build. In addition, if the air flow is small, a heat exchanger can also be used to heat the air. In short, the system can ensure the provision of high-temperature and high-pressure air.

[0061] The beneficial effects of the present invention are as follows:

[0062] The present invention constructs a convective heat exchange environment of fuel and air under active thermal protection conditions of the engine through a combination of an internal circular tube, an external cavity, a thermal insulation material, an air thermocouple and an infrared thermal imager. It can not only obtain convective heat transfer experimental data under specific conditions, but also is suitable for simulation calculation of convective heat transfer coefficient and flow resistance under the third type of boundary conditions, providing equipment support for precise thermal management of active cooling in the engine.

[0063] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0064] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A supercritical hydrocarbon fuel heat exchange simulation device for evaluating the third type of boundary conditions, characterized in that: include: An air compressor, an air heater, an inlet monitoring component, an experimental module, an outlet component, a water cooler and an air flow meter are connected in sequence; the experimental module includes: an internal round tube, an external cavity, a heat-insulating material, an air outlet thermocouple, a plurality of temperature measuring grooves, a plurality of air thermocouples, an infrared window and an infrared thermal imager; All the air thermocouples are fixed at equal intervals and depths on the outer surface of the external cavity; the air outlet thermocouples are arranged at the outlet position of the external cavity; the temperature measuring grooves are arranged at equal intervals on the surface of the internal round tube; the heat preservation material is arranged on the surface of the internal round tube corresponding to the air outlet thermocouples; the experimental module is cylindrical with both ends partially closed; the infrared window is arranged on the side of the external cavity; the infrared thermal imager is arranged outside the external cavity; The air compressor is used to reduce the compression of external air to the target pressure; the air heater is used to heat the high-pressure gas output by the air compressor to a preset temperature; the import monitoring components are used to collect input gas data; the export components are used to collect output gas data; the water cooler is used to cool the gas output by the experimental module; the air flow meter is used to count the air flow data; the air outlet thermocouple is used to measure the average temperature of the outlet of the experimental module using the insulation material; the air thermocouple is used to collect temperature data of preset points through the temperature measuring groove; the infrared thermal imager collects temperature data of the internal circular tube through the infrared window.

2. A supercritical hydrocarbon fuel heat exchange simulation device for evaluating the third type of boundary conditions according to claim 1, characterized in that: The internal flow medium of the inner circular tube is fuel oil with a maximum cracking temperature of 800K; the flow direction of the fuel oil is opposite to that of the gas flowing in the outer cavity.

3. A supercritical hydrocarbon fuel heat exchange simulation device for evaluating the third type of boundary conditions according to claim 1, characterized in that: The outer side of the external cavity is coated with a heat insulating material.

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